An existing liquid crystal display panel includes a plurality of pixel units, and a gate driving circuit and a source driving circuit for driving the pixel units to work. In this case, the gate driving circuit includes multi-stage gate driving units, and these gate driving units successively output gate signals through gate lines coupled thereto to control actuation of corresponding switch transistors in a display area, such that data signals output by the source driving circuit are written into the related pixel units to perform image display. Therefore, the operation reliability of the gate driving units has a vital influence on accuracy of imaging.
At present, the gate driving units of the gate driving circuit used by mainstream liquid crystal display panel manufacturers have had a substantially same structure, and may be divided into a plurality of functional modules, such as an actuating unit, an energy storage unit, a pull-up unit, a first pull-down unit and a second pull-down unit, in terms of their functions. These functional modules cooperate with one another under the action of time pulse signals and output gate signals based on input actuation signals and supply it to the related pixel units.
With development of manufacturing process, the existing gate driving circuit may be directly prepared on an array substrate, i.e., it is manufactured to be a circuit with gate driving circuit on array substrate (GOA circuit), and each switch element in the GOA circuit is made of a thin-film transistor. The thin-film transistor is turned on as long as under the condition that, similar to that of a field-effect transistor, the voltage difference of the gate and the source is greater than a threshold voltage. That is, the thin-film transistor could be turned on only when the difference between the gate voltage and the source voltage is greater than the threshold voltage. However, with the increase of the operation time of the thin-film transistor, the threshold voltage of the thin-film transistor is changed, that is, a threshold voltage offset phenomenon may occur.
For example, the threshold voltage of one thin-film transistor is 2V when under a normal condition, but it may offset by +5V with the increase of the operation time. At this time, the thin-film transistor may not be turned on but until the voltage difference of the gate and the source was more than or equal to 7V. Thus, it could be seen that the threshold voltage offset phenomenon of the thin-film transistor may seriously affect the operation performance of the thin-film transistor and thereby affect the operation performance of the gate driving circuit including the thin-film transistor. For example, with the increase of the operation time, if the threshold voltage of the thin-film transistor at the output end of one gate driving unit offsets and the turn-on voltage supplied to the thin-film transistor is still maintained to the turn-on voltage under the normal condition and never changed all the time, then the thin-film transistor would not be normally turned on, such that the gate driving unit can not normally output the gate signal, thus affecting normal display of the liquid crystal display panel.